Research suggests that adolescents often perceive parental behaviors—such as expressions of warmth and affection—differently than their parents do. These parent–adolescent discrepancies offer meaningful insight into family functioning during adolescence and adolescent mental health, though existing findings remain mixed. Grounded in interpersonal acceptance–rejection theory (IPARTheory), this study investigates longitudinal, bidirectional associations between parent–adolescent discrepancies in perceived parental warmth and adolescent internalizing symptoms. The sample included 1219 parent–adolescent dyads (both mothers and fathers) from 12 cultural groups across 9countries, followed across three time points spanning 5 years, with children's mean age being 10.72 years (SD = 0.67) at Wave 1, 13.19 years (SD = 0.90) at Wave 2, and 15.60 years (SD = 0.94) at Wave 3. The results of latent congruence models showed that mothers reported higher warmth than adolescents, whereas no significant discrepancies emerged between fathers and adolescents. The cross-sectional analyses indicated that a higher parent–adolescent discrepancy in parental warmth perceptions was linked to increased internalizing symptoms in adolescents and lower overall warmth perceived by parents and adolescents in the dyad. However, over the long term, marginal effects were observed only between greater internalizing symptoms in adolescents and lower overall warmth experienced, and vice versa. Additionally, some cross-cultural differences in the discrepancies between parents and adolescents were identified. These findings highlight the importance of congruence between parents' and adolescents' perceptions of parental warmth, which may play a critical role in reducing adolescent internalizing symptoms, at least in the short term. Future research should deepen these dynamics across different cultures and developmental stages to improve intervention strategies and strengthen family-based mental health support.